Many lists of "wonders of the world" are said to have existed during the Middle Ages, although it is unlikely that these lists originated at that time because the word medieval was not even invented until the Enlightenment-era, and the concept of a "Middle Age" did not become popular until the 16th century. Brewer's refers to them as "later list[s]" suggesting the lists were created after the Middle Ages.

Many of the structures on these lists were built much earlier than the Medieval Ages, but were well known. These lists go by names such as "Wonders of the Middle Ages" (implying no specific limitation to seven), "Seven Wonders of the Middle Ages", "Medieval Mind" and "Architectural Wonders of the Middle Ages".

Typically representative of the seven greatest wonders of the Medieval world are:

• Stonehenge
• Colosseum
• Catacombs of Kom el Shoqafa
• Great Wall of China
• Porcelain Tower of Nanjing
• Hagia Sophia
• Leaning Tower of Pisa

Other sites included on such lists:

• Taj Mahal
• Cairo Citadel
• Ely Cathedral
• Cluny Abbey

The historian Herodotus (484 BC–ca. 425 BC), and the scholar Callimachus of Cyrene (ca 305–240 BC) at the Museum of Alexandria, made early lists of "Seven wonders" but their writings have not survived, except as references. Their wonders included:

• Great Pyramid of Giza
• Hanging Gardens of Babylon
• Statue of Zeus at Olympia
• Temple of Artemis at Ephesus
• Mausoleum of Maussollos at Halicarnassus
• Colossus of Rhodes
• Lighthouse of Alexandria

The Greek category was not "Wonders" but "theamata", which translates closer to "must-sees". The list that we know today was compiled in the Middle Ages—by which time many of the sites were no longer in existence. Today, the only ancient world wonder that still exists is the Great Pyramid of Giza.

Inhabited since prehistoric times, this Nabataean caravan-city, situated between the Red Sea and the Dead Sea, was an important crossroads between Arabia, Egypt and Syria-Phoenicia. Petra is half-built, half-carved into the rock, and is surrounded by mountains riddled with passages and gorges. It is one of the world's most famous archaeological sites, where ancient Eastern traditions blend with Hellenistic architecture.

The United Nations Educational, Scientific and Cultural Organization (UNESCO) seeks to encourage the identification, protection and preservation of cultural and natural heritage around the world considered to be of outstanding value to humanity. This is embodied in an international treaty called the Convention concerning the Protection of the World Cultural and Natural Heritage, adopted by UNESCO in 1972.

UNESCO's World Heritage mission is to:

• encourage countries to sign the World Heritage Convention and to ensure the protection of their natural and cultural heritage;
• encourage States Parties to the Convention to nominate sites within their national territory for inclusion on the World Heritage List;
• encourage States Parties to establish management plans and set up reporting systems on the state of conservation of their World Heritage sites;
• help States Parties safeguard World Heritage properties by providing technical assistance and professional training;
• provide emergency assistance for World Heritage sites in immediate danger;
• support States Parties' public awareness-building activities for World Heritage conservation;
• encourage participation of the local population in the preservation of their cultural and natural heritage;
• encourage international cooperation in the conservation of our world's cultural and natural heritage.

You can read more about Petra as a UNESCO World Heritage Site at: http://whc.unesco.org/en/list/326